Help Monitor the Red Crossbill Invasion
by Nate Swick
Birders in the eastern part of the continent are calling this the best winter finch winter in decades, perhaps even more amazing in that it's not even officially winter yet! Beautiful and charismatic, Evening Grosbeaks are the centerpiece of this irruption, and we recently encouraged birders seeing "Evebeaks" to be sure to get those sightings reported to eBird so that we can watch the invasion happen in real-time.
Second only to the grosbeaks in inducing excitement with their arrival are the crossbills, both White-winged and Red, that have been sweeping across the east in incredible numbers. Much has been made of the fact that within the enigmatic species known as Red Crossbill may lie up to 10 cryptic, but full in their own right, species differentiated from one another by bill size, food preferences, and, especially, flight calls. Indeed, many of these "types" can be confidently identified by birders paying attention to those calls.
This season has seen reports of multiple types of Red Crossbills wherever the species has been reported. North American Birds editor Ned Brinkley, who is based on the eastern shore of Virginia, reports that both Type 3 and Type 10 crossbills have turned up in that state this fall, neither of which have ever been recorded in the past.
Now, asking birders to note the high-pitched mutterings of birds passing overhead may sound like a sure-fire way of deadening the joy in seeing these infrequent winter visitors, but an enormous amount of information can be acquired during these finch years from regular birders noting the sounds they hear from the bird they're seeing. Even something as simple as obtaining a recording can be a big deal, and these days most cell phones are capable of picking one up one of sufficient quality to make the ID.
Matt Young at Cornell Lab of Ornithology has been doing great work trying to suss out the differences in Red Crossbill populations. Earlier this fall, Matt wrote a primer posted to the eBird website laying out the differences with several incredibly useful audio examples. Matt also encourages birders who have recorded crossbills but need a hand identifying them to type to send those recordings to him at may6 AT cornell DOT edu.
Additionally, the ABA's journal of ornithological record, North American Birds, has been on the forefront of the crossbill ID revolution with several articles, by none other than Matt Young, focusing on status, distribution, and identification of the various types. Those posts, now suddenly exceedingly relevant, are now hosted free on the ABA site.
And although it scarcely needs to be said anymore, be sure to get those sightings entered into eBird. Our knowledge of irruptive boreal finches is woefully incompletely, but phenomena like these flights offer opportunities to make inroads into our gaps in knowledge.
Thanks, and enjoy the finches this winter!